Racial/ethnic and socioeconomic disparities in health care represent key contributors to racial/ethnic disparities in health. Although racial and ethnic disparities have been extensively documented across the continuum of health care, relatively little is known about the impact of HMOs on these disparities. On one hand, improved accountability for population-wide health care quality and strategies designed to constrain over-utilization may help HMOs to reduce disparities. On the other hand, more stringent cost containment efforts by HMOs may impose barriers to care for vulnerable populations. Under current HEDIS reporting requirements such disparities go undetected. The primary aim of this three-year project is to assess the scope and magnitude of racial/ethnic and socioeconomic disparities in HMOs. We will aggregate several years using the following national surveys: The Medical Expenditure Panel Survey, the National Ambulatory Medical Care Survey and National Hospital Ambulatory Care Survey, and the Healthcare Cost and Utilization Project. We will develop age, sex, and casemix adjusted utilization and quality measures that examine racial/ethnic and socioeconomic disparities in preventive care, satisfaction, change in health status, use of expensive hospital-based procedures, and avoidable hospital Complications and mortality. We will compare disparities in these measures between HMO and non-HMO members and assess changes overtime. Findings from this project should inform AHRQ's National Disparities Reporting. Because the measures will be derived from periodic national surveys, progress towards the elimination of disparities can be tracked over time using future iterations of these surveys and measures. If the study hypotheses are confirmed, the findings will underscore the need for HMOs to track and address disparities among their members if the Healthy People 2010 for the elimination of disparities is to be achieved.